As manufacturers of electronic devices seek to implement more efficient manufacturing processes, there has been a corresponding increase in the use of surface mounting in assembly operations. A typical electronic device may contain one or more circuit boards on which electrical and mechanical components are mounted. Many electrical components, such as power amplifiers and microprocessors, and some electro-mechanical components, such as connectors, are housed in packages which include leads to provide electrical connection from the component to the circuit board. Traditionally, leaded packages were mounted to a circuit board using through hole mounting techniques, which is well-suited to accommodate leads. Surface mounting technology has now replaced through hole mounting in many applications, in part to facilitate automation. However, there are certain problems associated with surface mounting leaded packages, especially when these leaded packages are surface mounted on a cladded printed circuit board. One such problem involves maintaining coplanarity among the leads on the leaded package.
Coplanarity exists among the leads on a package when the contact surfaces of the leads are substantially on the same plane. In a surface mounting operation, coplanarity is necessary to ensure that all the leads of the package make electrical contact with corresponding interface connections on the circuit board. A lack of coplanarity may be caused by several sources. For example, a leaded package manufacturer may be unable to consistently produce coplanar leads. Moreover, leads on a package may lose their coplanarity during normal handling. Consequently, defects may occur in an electronic device manufactured using non-coplanar leaded packages. For example, a leaded package will typically be soldered to a circuit board thereby becoming part of the electronic circuitry for the electronic device. If the leads on the package are even slightly non-coplanar, the package may be improperly seated on the circuit board thus causing poor or non-existent solder connections between the package and the circuit board. The result is an electronic device which may be defective and which will be more susceptible to mechanical and thermal stress failures.
A lack of lead coplanarity on surface mounted leaded packages is a major source of defects for many manufacturing operations. As more leaded packages are adapted for surface mounting, the need to eliminate coplanarity problems increases. The use of surface mounting in manufacturing can result in an improvement in manufacturing efficiency. Additionally, an improvement in product quality can be realized if the problem of lack of coplanarity of leaded packages can be addressed. Therefore, there exists a need for a new package design which addresses the coplanarity problem thereby facilitating the use of surface mounting.